In an optical module of an optical communication transceiver, an optical receptacle is used as a component for optically connecting an optical fiber connector to an optical element such as a light receiving element, a light emitting element, etc. (e.g., referring to Patent Document 1). Also, in optical communication, there are cases where multiple optical fiber connectors are connected to each other via an adapter without using an optical receptacle.
While the basic characteristic of the optical receptacle is to optically connect the optical element to the optical fiber connector as described above, among the characteristics, loss generally called the Wiggle loss is one important characteristic in which a transverse load applied to an optical fiber connector inserted into an optical receptacle causes shifting between the central axes of the fiber stub inside the optical receptacle and the plug ferrule inside the optical fiber connector.
Also, when the plug ferrule is initially inserted into the optical module including the optical receptacle, normally, cleaning of the end surfaces of the optical receptacle and the plug ferrule that are to be connected to each other is performed to avoid loss when connecting and avoid external appearance problems due to scratches made in the fiber.
Although a method for blowing off the foreign matter by air blowing and a method for wiping the foreign matter of the end surface using a cloth-like member such as that of Patent Document 2 are generally known as cleaning methods of the end surface of the optical receptacle to be connected to the plug ferrule, it is difficult to remove the foreign matter completely from the end surface because the end surface is at a position secluded from the tip portion of the optical receptacle; and the foreign matter is merely moved to the outer circumferential portion where there is little optical effect when connecting the plug ferrule.
Therefore, conventional optical receptacles have the problem of loss occurring when connecting due to the foreign matter at the outer circumferential portion of the fiber stub inside the optical receptacle moving to the central portion of the fiber stub in the process of repeatedly inserting and removing the plug ferrule. This problem occurs even in the case where multiple optical fiber connectors are connected to each other via an adapter. In other words, in the process of repeatedly inserting and removing one plug ferrule into and from the adapter, there is a problem of loss occurring due to the foreign matter at the outer circumferential portion of one other plug ferrule inside the adapter moving to the central portion when connecting the one plug ferrule and the one other plug ferrule.
In the case where the optical receptacle is used, to solve the problem recited above, a structure may be considered in which a stepped part is provided in the tip portion of the fiber stub to prevent the foreign matter at the outer circumferential portion moving to the central portion of the fiber stub in the process of repeatedly inserting and removing the plug ferrule into and from the optical receptacle (e.g., referring to Patent Document 3).
However, although the effects described above are obtained by the structure recited in Patent Document 3, there is a problem of the Wiggle loss described above undesirably increasing due to shortening of the length where the sleeve inside the optical receptacle holds the fiber stub.